The alleged hit squad was sent from Saudi Arabia and organized the killing.
Europe's largest economies - Britain, France and Germany - too said on Sunday that they were treating the case with "the utmost seriousness".
Erdogan and King Salman spoke by telephone on Sunday evening and stressed the importance of the two countries creating the joint working group as part of the investigation.
The Saudi stock exchange, only months earlier viewed as a darling of frontier investors, plunged as much as 7 per cent at one point Sunday before closing down over 4 per cent.
The moves by the US executives follow similar withdrawals from the event by JP Morgan & Chase Co Chief Executive Jamie Dimon and Ford Motor Co Chairman Bill Ford on Sunday. The market clawed back some of the losses, closing down 3.5 per cent for the day.
Brent crude, the benchmark for more than half the world's oil, rose as much as 1.9 percent to $81.92 a barrel, before paring gains to trade at $81.24 by 6:58 a.m.in London. But then, if they cared about such realities, the US would have cut off support to the Saudi war in Yemen years ago.
The crown prince, ambitious, aggressive and just 33 in a kingdom long ruled by aging monarchs, has considerable weight in Saudi government actions.
"The kingdom's economy has an influential and vital role in the global economy, and that kingdom's economy is only affected by the global economy". Uber CEO Dara Khosrowshahi, former AOL CEO and venture capitalist Steve Case, and Google Android creator Andy Rubin all pulled out last week after multiple reports linked the disappearance of Washington Post columnist Jamal Khashoggi in Turkey to the Saudi government after he failed to emerge from a visit to the Saudi embassy in Istanbul, according to Bloomberg.
Trump has repeatedly criticized Saudi Arabia and King Salman over rising global oil prices.
Saudi authorities last week agreed to let Turkish officials search the consulate after Ankara sought permission to probe the building on Saudi sovereign territory.
Meanwhile, Saudi Arabia warned it would retaliate against any sanctions imposed on the oil-rich kingdom over the disappearance of Khashoggi, as more Western companies distanced themselves from the Gulf State. The CEOs of both corporations cited the uncertainty related to the recent disappearance of a Saudi dissident in Istanbul, Turkey, and concerns that the Trump administration may take diplomatic action against the kingdom.
Saudi Arabia's Public Investment Fund which hosts the conference, has tentatively committed $20 billion to an infrastructure investment planned with Blackstone Group.
The three-day event will be held next week and is also meant to showcase Prince Mohammed bin Salman's modernization plan for the desert kingdom.
Those policies are all seen as initiatives of the crown prince, who has also presided over a roundup of activists and businessmen.